// List implementation -*- C++ -*-

// Copyright (C) 2001-2015 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/*
 *
 * Copyright (c) 1994
 * Hewlett-Packard Company
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Hewlett-Packard Company makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 *
 * Copyright (c) 1996,1997
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 */

 /** @file bits/stl_list.h
  *  This is an internal header file, included by other library headers.
  *  Do not attempt to use it directly. @headername{list}
  */

#ifndef _STL_LIST_H
#define _STL_LIST_H 1

#include <bits/concept_check.h>
#if __cplusplus >= 201103L
#include <initializer_list>
#endif

namespace std _GLIBCXX_VISIBILITY(default)
{
    namespace __detail
    {
        _GLIBCXX_BEGIN_NAMESPACE_VERSION

            // Supporting structures are split into common and templated
            // types; the latter publicly inherits from the former in an
            // effort to reduce code duplication.  This results in some
            // "needless" static_cast'ing later on, but it's all safe
            // downcasting.

            /// Common part of a node in the %list. 
            struct _List_node_base
        {
            _List_node_base* _M_next;
            _List_node_base* _M_prev;

            static void
                swap(_List_node_base& __x, _List_node_base& __y) _GLIBCXX_USE_NOEXCEPT;

            void
                _M_transfer(_List_node_base* const __first,
                    _List_node_base* const __last) _GLIBCXX_USE_NOEXCEPT;

            void
                _M_reverse() _GLIBCXX_USE_NOEXCEPT;

            void
                _M_hook(_List_node_base* const __position) _GLIBCXX_USE_NOEXCEPT;

            void
                _M_unhook() _GLIBCXX_USE_NOEXCEPT;
        };

        _GLIBCXX_END_NAMESPACE_VERSION
    } // namespace detail

    _GLIBCXX_BEGIN_NAMESPACE_CONTAINER

        /// An actual node in the %list.
        template<typename _Tp>
    struct _List_node : public __detail::_List_node_base
    {
        ///< User's data.
        _Tp _M_data;

#if __cplusplus >= 201103L
        template<typename... _Args>
        _List_node(_Args&&... __args)
            : __detail::_List_node_base(), _M_data(std::forward<_Args>(__args)...)
        { }
#endif
    };

    /**
     *  @brief A list::iterator.
     *
     *  All the functions are op overloads.
    */
    template<typename _Tp>
    struct _List_iterator
    {
        typedef _List_iterator<_Tp>                _Self;
        typedef _List_node<_Tp>                    _Node;

        typedef ptrdiff_t                          difference_type;
        typedef std::bidirectional_iterator_tag    iterator_category;
        typedef _Tp                                value_type;
        typedef _Tp* pointer;
        typedef _Tp& reference;

        _List_iterator() _GLIBCXX_NOEXCEPT
            : _M_node() { }

        explicit
            _List_iterator(__detail::_List_node_base* __x) _GLIBCXX_NOEXCEPT
            : _M_node(__x) { }

        _Self
            _M_const_cast() const _GLIBCXX_NOEXCEPT
        {
            return *this;
        }

        // Must downcast from _List_node_base to _List_node to get to _M_data.
        reference
            operator*() const _GLIBCXX_NOEXCEPT
        {
            return static_cast<_Node*>(_M_node)->_M_data;
        }

        pointer
            operator->() const _GLIBCXX_NOEXCEPT
        {
            return std::__addressof(static_cast<_Node*>(_M_node)->_M_data);
        }

        _Self&
            operator++() _GLIBCXX_NOEXCEPT
        {
            _M_node = _M_node->_M_next;
            return *this;
        }

        _Self
            operator++(int) _GLIBCXX_NOEXCEPT
        {
            _Self __tmp = *this;
            _M_node = _M_node->_M_next;
            return __tmp;
        }

        _Self&
            operator--() _GLIBCXX_NOEXCEPT
        {
            _M_node = _M_node->_M_prev;
            return *this;
        }

        _Self
            operator--(int) _GLIBCXX_NOEXCEPT
        {
            _Self __tmp = *this;
            _M_node = _M_node->_M_prev;
            return __tmp;
        }

        bool
            operator==(const _Self& __x) const _GLIBCXX_NOEXCEPT
        {
            return _M_node == __x._M_node;
        }

        bool
            operator!=(const _Self& __x) const _GLIBCXX_NOEXCEPT
        {
            return _M_node != __x._M_node;
        }

        // The only member points to the %list element.
        __detail::_List_node_base* _M_node;
    };

    /**
     *  @brief A list::const_iterator.
     *
     *  All the functions are op overloads.
    */
    template<typename _Tp>
    struct _List_const_iterator
    {
        typedef _List_const_iterator<_Tp>          _Self;
        typedef const _List_node<_Tp>              _Node;
        typedef _List_iterator<_Tp>                iterator;

        typedef ptrdiff_t                          difference_type;
        typedef std::bidirectional_iterator_tag    iterator_category;
        typedef _Tp                                value_type;
        typedef const _Tp* pointer;
        typedef const _Tp& reference;

        _List_const_iterator() _GLIBCXX_NOEXCEPT
            : _M_node() { }

        explicit
            _List_const_iterator(const __detail::_List_node_base* __x)
            _GLIBCXX_NOEXCEPT
            : _M_node(__x) { }

        _List_const_iterator(const iterator& __x) _GLIBCXX_NOEXCEPT
            : _M_node(__x._M_node) { }

        iterator
            _M_const_cast() const _GLIBCXX_NOEXCEPT
        {
            return iterator(const_cast<__detail::_List_node_base*>(_M_node));
        }

        // Must downcast from List_node_base to _List_node to get to
        // _M_data.
        reference
            operator*() const _GLIBCXX_NOEXCEPT
        {
            return static_cast<_Node*>(_M_node)->_M_data;
        }

        pointer
            operator->() const _GLIBCXX_NOEXCEPT
        {
            return std::__addressof(static_cast<_Node*>(_M_node)->_M_data);
        }

        _Self&
            operator++() _GLIBCXX_NOEXCEPT
        {
            _M_node = _M_node->_M_next;
            return *this;
        }

        _Self
            operator++(int) _GLIBCXX_NOEXCEPT
        {
            _Self __tmp = *this;
            _M_node = _M_node->_M_next;
            return __tmp;
        }

        _Self&
            operator--() _GLIBCXX_NOEXCEPT
        {
            _M_node = _M_node->_M_prev;
            return *this;
        }

        _Self
            operator--(int) _GLIBCXX_NOEXCEPT
        {
            _Self __tmp = *this;
            _M_node = _M_node->_M_prev;
            return __tmp;
        }

        bool
            operator==(const _Self& __x) const _GLIBCXX_NOEXCEPT
        {
            return _M_node == __x._M_node;
        }

        bool
            operator!=(const _Self& __x) const _GLIBCXX_NOEXCEPT
        {
            return _M_node != __x._M_node;
        }

        // The only member points to the %list element.
        const __detail::_List_node_base* _M_node;
    };

    template<typename _Val>
    inline bool
        operator==(const _List_iterator<_Val>&__x,
            const _List_const_iterator<_Val>&__y) _GLIBCXX_NOEXCEPT
    {
        return __x._M_node == __y._M_node;
    }

    template<typename _Val>
    inline bool
        operator!=(const _List_iterator<_Val>&__x,
            const _List_const_iterator<_Val>&__y) _GLIBCXX_NOEXCEPT
    {
        return __x._M_node != __y._M_node;
    }

    _GLIBCXX_BEGIN_NAMESPACE_CXX11
        /// See bits/stl_deque.h's _Deque_base for an explanation.
        template<typename _Tp, typename _Alloc>
    class _List_base
    {
    protected:
        // NOTA BENE
        // The stored instance is not actually of "allocator_type"'s
        // type.  Instead we rebind the type to
        // Allocator<List_node<Tp>>, which according to [20.1.5]/4
        // should probably be the same.  List_node<Tp> is not the same
        // size as Tp (it's two pointers larger), and specializations on
        // Tp may go unused because List_node<Tp> is being bound
        // instead.
        //
        // We put this to the test in the constructors and in
        // get_allocator, where we use conversions between
        // allocator_type and _Node_alloc_type. The conversion is
        // required by table 32 in [20.1.5].
        typedef typename _Alloc::template rebind<_List_node<_Tp> >::other
            _Node_alloc_type;

        typedef typename _Alloc::template rebind<_Tp>::other _Tp_alloc_type;

        static size_t
            _S_distance(const __detail::_List_node_base* __first,
                const __detail::_List_node_base* __last)
        {
            size_t __n = 0;
            while (__first != __last)
            {
                __first = __first->_M_next;
                ++__n;
            }
            return __n;
        }

        struct _List_impl
            : public _Node_alloc_type
        {
#if _GLIBCXX_USE_CXX11_ABI
            _List_node<size_t> _M_node;
#else
            __detail::_List_node_base _M_node;
#endif

            _List_impl()
                : _Node_alloc_type(), _M_node()
            { }

            _List_impl(const _Node_alloc_type& __a) _GLIBCXX_NOEXCEPT
                : _Node_alloc_type(__a), _M_node()
            { }

#if __cplusplus >= 201103L
            _List_impl(_Node_alloc_type&& __a) _GLIBCXX_NOEXCEPT
                : _Node_alloc_type(std::move(__a)), _M_node()
            { }
#endif
        };

        _List_impl _M_impl;

#if _GLIBCXX_USE_CXX11_ABI
        size_t _M_get_size() const { return _M_impl._M_node._M_data; }

        void _M_set_size(size_t __n) { _M_impl._M_node._M_data = __n; }

        void _M_inc_size(size_t __n) { _M_impl._M_node._M_data += __n; }

        void _M_dec_size(size_t __n) { _M_impl._M_node._M_data -= __n; }

        size_t
            _M_distance(const __detail::_List_node_base* __first,
                const __detail::_List_node_base* __last) const
        {
            return _S_distance(__first, __last);
        }

        // return the stored size
        size_t _M_node_count() const { return _M_impl._M_node._M_data; }
#else
        // dummy implementations used when the size is not stored
        size_t _M_get_size() const { return 0; }
        void _M_set_size(size_t) { }
        void _M_inc_size(size_t) { }
        void _M_dec_size(size_t) { }
        size_t _M_distance(const void*, const void*) const { return 0; }

        // count the number of nodes
        size_t _M_node_count() const
        {
            return _S_distance(_M_impl._M_node._M_next,
                std::__addressof(_M_impl._M_node));
        }
#endif

        _List_node<_Tp>*
            _M_get_node()
        {
            return _M_impl._Node_alloc_type::allocate(1);
        }

        void
            _M_put_node(_List_node<_Tp>* __p) _GLIBCXX_NOEXCEPT
        {
            _M_impl._Node_alloc_type::deallocate(__p, 1);
        }

    public:
        typedef _Alloc allocator_type;

        _Node_alloc_type&
            _M_get_Node_allocator() _GLIBCXX_NOEXCEPT
        {
            return *static_cast<_Node_alloc_type*>(&_M_impl);
        }

        const _Node_alloc_type&
            _M_get_Node_allocator() const _GLIBCXX_NOEXCEPT
        {
            return *static_cast<const _Node_alloc_type*>(&_M_impl);
        }

        _Tp_alloc_type
            _M_get_Tp_allocator() const _GLIBCXX_NOEXCEPT
        {
            return _Tp_alloc_type(_M_get_Node_allocator());
        }

        allocator_type
            get_allocator() const _GLIBCXX_NOEXCEPT
        {
            return allocator_type(_M_get_Node_allocator());
        }

        _List_base()
            : _M_impl()
        {
            _M_init();
        }

        _List_base(const _Node_alloc_type& __a) _GLIBCXX_NOEXCEPT
            : _M_impl(__a)
        {
            _M_init();
        }

#if __cplusplus >= 201103L
        _List_base(_List_base&& __x) noexcept
            : _M_impl(std::move(__x._M_get_Node_allocator()))
        {
            auto* const __xnode = std::__addressof(__x._M_impl._M_node);
            if (__xnode->_M_next == __xnode)
                _M_init();
            else
            {
                auto* const __node = std::__addressof(_M_impl._M_node);
                __node->_M_next = __xnode->_M_next;
                __node->_M_prev = __xnode->_M_prev;
                __node->_M_next->_M_prev = __node->_M_prev->_M_next = __node;
                _M_set_size(__x._M_get_size());
                __x._M_init();
            }
        }
#endif

        // This is what actually destroys the list.
        ~_List_base() _GLIBCXX_NOEXCEPT
        {
            _M_clear();
        }

        void
            _M_clear() _GLIBCXX_NOEXCEPT;

        void
            _M_init() _GLIBCXX_NOEXCEPT
        {
            this->_M_impl._M_node._M_next = &this->_M_impl._M_node;
            this->_M_impl._M_node._M_prev = &this->_M_impl._M_node;
            _M_set_size(0);
        }
    };

    /**
     *  @brief A standard container with linear time access to elements,
     *  and fixed time insertion/deletion at any point in the sequence.
     *
     *  @ingroup sequences
     *
     *  @tparam _Tp  Type of element.
     *  @tparam _Alloc  Allocator type, defaults to allocator<_Tp>.
     *
     *  Meets the requirements of a <a href="tables.html#65">container</a>, a
     *  <a href="tables.html#66">reversible container</a>, and a
     *  <a href="tables.html#67">sequence</a>, including the
     *  <a href="tables.html#68">optional sequence requirements</a> with the
     *  %exception of @c at and @c operator[].
     *
     *  This is a @e doubly @e linked %list.  Traversal up and down the
     *  %list requires linear time, but adding and removing elements (or
     *  @e nodes) is done in constant time, regardless of where the
     *  change takes place.  Unlike std::vector and std::deque,
     *  random-access iterators are not provided, so subscripting ( @c
     *  [] ) access is not allowed.  For algorithms which only need
     *  sequential access, this lack makes no difference.
     *
     *  Also unlike the other standard containers, std::list provides
     *  specialized algorithms %unique to linked lists, such as
     *  splicing, sorting, and in-place reversal.
     *
     *  A couple points on memory allocation for list<Tp>:
     *
     *  First, we never actually allocate a Tp, we allocate
     *  List_node<Tp>'s and trust [20.1.5]/4 to DTRT.  This is to ensure
     *  that after elements from %list<X,Alloc1> are spliced into
     *  %list<X,Alloc2>, destroying the memory of the second %list is a
     *  valid operation, i.e., Alloc1 giveth and Alloc2 taketh away.
     *
     *  Second, a %list conceptually represented as
     *  @code
     *    A <---> B <---> C <---> D
     *  @endcode
     *  is actually circular; a link exists between A and D.  The %list
     *  class holds (as its only data member) a private list::iterator
     *  pointing to @e D, not to @e A!  To get to the head of the %list,
     *  we start at the tail and move forward by one.  When this member
     *  iterator's next/previous pointers refer to itself, the %list is
     *  %empty.
    */
    template<typename _Tp, typename _Alloc = std::allocator<_Tp> >
    class list : protected _List_base<_Tp, _Alloc>
    {
        // concept requirements
        typedef typename _Alloc::value_type                _Alloc_value_type;
        __glibcxx_class_requires(_Tp, _SGIAssignableConcept)
            __glibcxx_class_requires2(_Tp, _Alloc_value_type, _SameTypeConcept)

            typedef _List_base<_Tp, _Alloc>                    _Base;
        typedef typename _Base::_Tp_alloc_type		 _Tp_alloc_type;
        typedef typename _Base::_Node_alloc_type		 _Node_alloc_type;

    public:
        typedef _Tp                                        value_type;
        typedef typename _Tp_alloc_type::pointer           pointer;
        typedef typename _Tp_alloc_type::const_pointer     const_pointer;
        typedef typename _Tp_alloc_type::reference         reference;
        typedef typename _Tp_alloc_type::const_reference   const_reference;
        typedef _List_iterator<_Tp>                        iterator;
        typedef _List_const_iterator<_Tp>                  const_iterator;
        typedef std::reverse_iterator<const_iterator>      const_reverse_iterator;
        typedef std::reverse_iterator<iterator>            reverse_iterator;
        typedef size_t                                     size_type;
        typedef ptrdiff_t                                  difference_type;
        typedef _Alloc                                     allocator_type;

    protected:
        // Note that pointers-to-_Node's can be ctor-converted to
        // iterator types.
        typedef _List_node<_Tp>				 _Node;

        using _Base::_M_impl;
        using _Base::_M_put_node;
        using _Base::_M_get_node;
        using _Base::_M_get_Tp_allocator;
        using _Base::_M_get_Node_allocator;

        /**
         *  @param  __args  An instance of user data.
         *
         *  Allocates space for a new node and constructs a copy of
         *  @a __args in it.
         */
#if __cplusplus < 201103L
        _Node*
            _M_create_node(const value_type& __x)
        {
            _Node* __p = this->_M_get_node();
            __try
            {
                _M_get_Tp_allocator().construct
                (std::__addressof(__p->_M_data), __x);
            }
            __catch(...)
            {
                _M_put_node(__p);
                __throw_exception_again;
            }
            return __p;
        }
#else
        template<typename... _Args>
        _Node*
            _M_create_node(_Args&&... __args)
        {
            _Node* __p = this->_M_get_node();
            __try
            {
                _M_get_Node_allocator().construct(__p,
                    std::forward<_Args>(__args)...);
            }
            __catch(...)
            {
                _M_put_node(__p);
                __throw_exception_again;
            }
            return __p;
        }
#endif

    public:
        // [23.2.2.1] construct/copy/destroy
        // (assign() and get_allocator() are also listed in this section)

        /**
         *  @brief  Creates a %list with no elements.
         */
        list()
#if __cplusplus >= 201103L
            noexcept(is_nothrow_default_constructible<_Node_alloc_type>::value)
#endif
            : _Base() { }

        /**
         *  @brief  Creates a %list with no elements.
         *  @param  __a  An allocator object.
         */
        explicit
            list(const allocator_type& __a) _GLIBCXX_NOEXCEPT
            : _Base(_Node_alloc_type(__a)) { }

#if __cplusplus >= 201103L
        /**
         *  @brief  Creates a %list with default constructed elements.
         *  @param  __n  The number of elements to initially create.
         *
         *  This constructor fills the %list with @a __n default
         *  constructed elements.
         */
        explicit
            list(size_type __n)
            : _Base()
        {
            _M_default_initialize(__n);
        }

        /**
         *  @brief  Creates a %list with copies of an exemplar element.
         *  @param  __n  The number of elements to initially create.
         *  @param  __value  An element to copy.
         *  @param  __a  An allocator object.
         *
         *  This constructor fills the %list with @a __n copies of @a __value.
         */
        list(size_type __n, const value_type& __value,
            const allocator_type& __a = allocator_type())
            : _Base(_Node_alloc_type(__a))
        {
            _M_fill_initialize(__n, __value);
        }
#else
        /**
         *  @brief  Creates a %list with copies of an exemplar element.
         *  @param  __n  The number of elements to initially create.
         *  @param  __value  An element to copy.
         *  @param  __a  An allocator object.
         *
         *  This constructor fills the %list with @a __n copies of @a __value.
         */
        explicit
            list(size_type __n, const value_type& __value = value_type(),
                const allocator_type& __a = allocator_type())
            : _Base(_Node_alloc_type(__a))
        {
            _M_fill_initialize(__n, __value);
        }
#endif

        /**
         *  @brief  %List copy constructor.
         *  @param  __x  A %list of identical element and allocator types.
         *
         *  The newly-created %list uses a copy of the allocation object used
         *  by @a __x.
         */
        list(const list& __x)
            : _Base(__x._M_get_Node_allocator())
        {
            _M_initialize_dispatch(__x.begin(), __x.end(), __false_type());
        }

#if __cplusplus >= 201103L
        /**
         *  @brief  %List move constructor.
         *  @param  __x  A %list of identical element and allocator types.
         *
         *  The newly-created %list contains the exact contents of @a __x.
         *  The contents of @a __x are a valid, but unspecified %list.
         */
        list(list&& __x) noexcept
            : _Base(std::move(__x)) { }

        /**
         *  @brief  Builds a %list from an initializer_list
         *  @param  __l  An initializer_list of value_type.
         *  @param  __a  An allocator object.
         *
         *  Create a %list consisting of copies of the elements in the
         *  initializer_list @a __l.  This is linear in __l.size().
         */
        list(initializer_list<value_type> __l,
            const allocator_type& __a = allocator_type())
            : _Base(_Node_alloc_type(__a))
        {
            _M_initialize_dispatch(__l.begin(), __l.end(), __false_type());
        }
#endif

        /**
         *  @brief  Builds a %list from a range.
         *  @param  __first  An input iterator.
         *  @param  __last  An input iterator.
         *  @param  __a  An allocator object.
         *
         *  Create a %list consisting of copies of the elements from
         *  [@a __first,@a __last).  This is linear in N (where N is
         *  distance(@a __first,@a __last)).
         */
#if __cplusplus >= 201103L
        template<typename _InputIterator,
            typename = std::_RequireInputIter<_InputIterator>>
            list(_InputIterator __first, _InputIterator __last,
                const allocator_type& __a = allocator_type())
            : _Base(_Node_alloc_type(__a))
        {
            _M_initialize_dispatch(__first, __last, __false_type());
        }
#else
        template<typename _InputIterator>
        list(_InputIterator __first, _InputIterator __last,
            const allocator_type& __a = allocator_type())
            : _Base(_Node_alloc_type(__a))
        {
            // Check whether it's an integral type.  If so, it's not an iterator.
            typedef typename std::__is_integer<_InputIterator>::__type _Integral;
            _M_initialize_dispatch(__first, __last, _Integral());
        }
#endif

        /**
         *  No explicit dtor needed as the _Base dtor takes care of
         *  things.  The _Base dtor only erases the elements, and note
         *  that if the elements themselves are pointers, the pointed-to
         *  memory is not touched in any way.  Managing the pointer is
         *  the user's responsibility.
         */

         /**
          *  @brief  %List assignment operator.
          *  @param  __x  A %list of identical element and allocator types.
          *
          *  All the elements of @a __x are copied, but unlike the copy
          *  constructor, the allocator object is not copied.
          */
        list&
            operator=(const list& __x);

#if __cplusplus >= 201103L
        /**
         *  @brief  %List move assignment operator.
         *  @param  __x  A %list of identical element and allocator types.
         *
         *  The contents of @a __x are moved into this %list (without copying).
         *  @a __x is a valid, but unspecified %list
         */
        list&
            operator=(list&& __x)
        {
            // NB: DR 1204.
            // NB: DR 675.
            this->clear();
            this->swap(__x);
            return *this;
        }

        /**
         *  @brief  %List initializer list assignment operator.
         *  @param  __l  An initializer_list of value_type.
         *
         *  Replace the contents of the %list with copies of the elements
         *  in the initializer_list @a __l.  This is linear in l.size().
         */
        list&
            operator=(initializer_list<value_type> __l)
        {
            this->assign(__l.begin(), __l.end());
            return *this;
        }
#endif

        /**
         *  @brief  Assigns a given value to a %list.
         *  @param  __n  Number of elements to be assigned.
         *  @param  __val  Value to be assigned.
         *
         *  This function fills a %list with @a __n copies of the given
         *  value.  Note that the assignment completely changes the %list
         *  and that the resulting %list's size is the same as the number
         *  of elements assigned.  Old data may be lost.
         */
        void
            assign(size_type __n, const value_type& __val)
        {
            _M_fill_assign(__n, __val);
        }

        /**
         *  @brief  Assigns a range to a %list.
         *  @param  __first  An input iterator.
         *  @param  __last   An input iterator.
         *
         *  This function fills a %list with copies of the elements in the
         *  range [@a __first,@a __last).
         *
         *  Note that the assignment completely changes the %list and
         *  that the resulting %list's size is the same as the number of
         *  elements assigned.  Old data may be lost.
         */
#if __cplusplus >= 201103L
        template<typename _InputIterator,
            typename = std::_RequireInputIter<_InputIterator>>
            void
            assign(_InputIterator __first, _InputIterator __last)
        {
            _M_assign_dispatch(__first, __last, __false_type());
        }
#else
        template<typename _InputIterator>
        void
            assign(_InputIterator __first, _InputIterator __last)
        {
            // Check whether it's an integral type.  If so, it's not an iterator.
            typedef typename std::__is_integer<_InputIterator>::__type _Integral;
            _M_assign_dispatch(__first, __last, _Integral());
        }
#endif

#if __cplusplus >= 201103L
        /**
         *  @brief  Assigns an initializer_list to a %list.
         *  @param  __l  An initializer_list of value_type.
         *
         *  Replace the contents of the %list with copies of the elements
         *  in the initializer_list @a __l.  This is linear in __l.size().
         */
        void
            assign(initializer_list<value_type> __l)
        {
            this->assign(__l.begin(), __l.end());
        }
#endif

        /// Get a copy of the memory allocation object.
        allocator_type
            get_allocator() const _GLIBCXX_NOEXCEPT
        {
            return _Base::get_allocator();
        }

        // iterators
        /**
         *  Returns a read/write iterator that points to the first element in the
         *  %list.  Iteration is done in ordinary element order.
         */
        iterator
            begin() _GLIBCXX_NOEXCEPT
        {
            return iterator(this->_M_impl._M_node._M_next);
        }

        /**
         *  Returns a read-only (constant) iterator that points to the
         *  first element in the %list.  Iteration is done in ordinary
         *  element order.
         */
        const_iterator
            begin() const _GLIBCXX_NOEXCEPT
        {
            return const_iterator(this->_M_impl._M_node._M_next);
        }

        /**
         *  Returns a read/write iterator that points one past the last
         *  element in the %list.  Iteration is done in ordinary element
         *  order.
         */
        iterator
            end() _GLIBCXX_NOEXCEPT
        {
            return iterator(&this->_M_impl._M_node);
        }

        /**
         *  Returns a read-only (constant) iterator that points one past
         *  the last element in the %list.  Iteration is done in ordinary
         *  element order.
         */
        const_iterator
            end() const _GLIBCXX_NOEXCEPT
        {
            return const_iterator(&this->_M_impl._M_node);
        }

        /**
         *  Returns a read/write reverse iterator that points to the last
         *  element in the %list.  Iteration is done in reverse element
         *  order.
         */
        reverse_iterator
            rbegin() _GLIBCXX_NOEXCEPT
        {
            return reverse_iterator(end());
        }

        /**
         *  Returns a read-only (constant) reverse iterator that points to
         *  the last element in the %list.  Iteration is done in reverse
         *  element order.
         */
        const_reverse_iterator
            rbegin() const _GLIBCXX_NOEXCEPT
        {
            return const_reverse_iterator(end());
        }

        /**
         *  Returns a read/write reverse iterator that points to one
         *  before the first element in the %list.  Iteration is done in
         *  reverse element order.
         */
        reverse_iterator
            rend() _GLIBCXX_NOEXCEPT
        {
            return reverse_iterator(begin());
        }

        /**
         *  Returns a read-only (constant) reverse iterator that points to one
         *  before the first element in the %list.  Iteration is done in reverse
         *  element order.
         */
        const_reverse_iterator
            rend() const _GLIBCXX_NOEXCEPT
        {
            return const_reverse_iterator(begin());
        }

#if __cplusplus >= 201103L
        /**
         *  Returns a read-only (constant) iterator that points to the
         *  first element in the %list.  Iteration is done in ordinary
         *  element order.
         */
        const_iterator
            cbegin() const noexcept
        {
            return const_iterator(this->_M_impl._M_node._M_next);
        }

        /**
         *  Returns a read-only (constant) iterator that points one past
         *  the last element in the %list.  Iteration is done in ordinary
         *  element order.
         */
        const_iterator
            cend() const noexcept
        {
            return const_iterator(&this->_M_impl._M_node);
        }

        /**
         *  Returns a read-only (constant) reverse iterator that points to
         *  the last element in the %list.  Iteration is done in reverse
         *  element order.
         */
        const_reverse_iterator
            crbegin() const noexcept
        {
            return const_reverse_iterator(end());
        }

        /**
         *  Returns a read-only (constant) reverse iterator that points to one
         *  before the first element in the %list.  Iteration is done in reverse
         *  element order.
         */
        const_reverse_iterator
            crend() const noexcept
        {
            return const_reverse_iterator(begin());
        }
#endif

        // [23.2.2.2] capacity
        /**
         *  Returns true if the %list is empty.  (Thus begin() would equal
         *  end().)
         */
        bool
            empty() const _GLIBCXX_NOEXCEPT
        {
            return this->_M_impl._M_node._M_next == &this->_M_impl._M_node;
        }

        /**  Returns the number of elements in the %list.  */
        size_type
            size() const _GLIBCXX_NOEXCEPT
        {
            return this->_M_node_count();
        }

        /**  Returns the size() of the largest possible %list.  */
        size_type
            max_size() const _GLIBCXX_NOEXCEPT
        {
            return _M_get_Node_allocator().max_size();
        }

#if __cplusplus >= 201103L
        /**
         *  @brief Resizes the %list to the specified number of elements.
         *  @param __new_size Number of elements the %list should contain.
         *
         *  This function will %resize the %list to the specified number
         *  of elements.  If the number is smaller than the %list's
         *  current size the %list is truncated, otherwise default
         *  constructed elements are appended.
         */
        void
            resize(size_type __new_size);

        /**
         *  @brief Resizes the %list to the specified number of elements.
         *  @param __new_size Number of elements the %list should contain.
         *  @param __x Data with which new elements should be populated.
         *
         *  This function will %resize the %list to the specified number
         *  of elements.  If the number is smaller than the %list's
         *  current size the %list is truncated, otherwise the %list is
         *  extended and new elements are populated with given data.
         */
        void
            resize(size_type __new_size, const value_type& __x);
#else
        /**
         *  @brief Resizes the %list to the specified number of elements.
         *  @param __new_size Number of elements the %list should contain.
         *  @param __x Data with which new elements should be populated.
         *
         *  This function will %resize the %list to the specified number
         *  of elements.  If the number is smaller than the %list's
         *  current size the %list is truncated, otherwise the %list is
         *  extended and new elements are populated with given data.
         */
        void
            resize(size_type __new_size, value_type __x = value_type());
#endif

        // element access
        /**
         *  Returns a read/write reference to the data at the first
         *  element of the %list.
         */
        reference
            front() _GLIBCXX_NOEXCEPT
        {
            return *begin();
        }

        /**
         *  Returns a read-only (constant) reference to the data at the first
         *  element of the %list.
         */
        const_reference
            front() const _GLIBCXX_NOEXCEPT
        {
            return *begin();
        }

        /**
         *  Returns a read/write reference to the data at the last element
         *  of the %list.
         */
        reference
            back() _GLIBCXX_NOEXCEPT
        {
            iterator __tmp = end();
            --__tmp;
            return *__tmp;
        }

        /**
         *  Returns a read-only (constant) reference to the data at the last
         *  element of the %list.
         */
        const_reference
            back() const _GLIBCXX_NOEXCEPT
        {
            const_iterator __tmp = end();
            --__tmp;
            return *__tmp;
        }

        // [23.2.2.3] modifiers
        /**
         *  @brief  Add data to the front of the %list.
         *  @param  __x  Data to be added.
         *
         *  This is a typical stack operation.  The function creates an
         *  element at the front of the %list and assigns the given data
         *  to it.  Due to the nature of a %list this operation can be
         *  done in constant time, and does not invalidate iterators and
         *  references.
         */
        void
            push_front(const value_type& __x)
        {
            this->_M_insert(begin(), __x);
        }

#if __cplusplus >= 201103L
        void
            push_front(value_type&& __x)
        {
            this->_M_insert(begin(), std::move(__x));
        }

        template<typename... _Args>
        void
            emplace_front(_Args&&... __args)
        {
            this->_M_insert(begin(), std::forward<_Args>(__args)...);
        }
#endif

        /**
         *  @brief  Removes first element.
         *
         *  This is a typical stack operation.  It shrinks the %list by
         *  one.  Due to the nature of a %list this operation can be done
         *  in constant time, and only invalidates iterators/references to
         *  the element being removed.
         *
         *  Note that no data is returned, and if the first element's data
         *  is needed, it should be retrieved before pop_front() is
         *  called.
         */
        void
            pop_front() _GLIBCXX_NOEXCEPT
        {
            this->_M_erase(begin());
        }

        /**
         *  @brief  Add data to the end of the %list.
         *  @param  __x  Data to be added.
         *
         *  This is a typical stack operation.  The function creates an
         *  element at the end of the %list and assigns the given data to
         *  it.  Due to the nature of a %list this operation can be done
         *  in constant time, and does not invalidate iterators and
         *  references.
         */
        void
            push_back(const value_type& __x)
        {
            this->_M_insert(end(), __x);
        }

#if __cplusplus >= 201103L
        void
            push_back(value_type&& __x)
        {
            this->_M_insert(end(), std::move(__x));
        }

        template<typename... _Args>
        void
            emplace_back(_Args&&... __args)
        {
            this->_M_insert(end(), std::forward<_Args>(__args)...);
        }
#endif

        /**
         *  @brief  Removes last element.
         *
         *  This is a typical stack operation.  It shrinks the %list by
         *  one.  Due to the nature of a %list this operation can be done
         *  in constant time, and only invalidates iterators/references to
         *  the element being removed.
         *
         *  Note that no data is returned, and if the last element's data
         *  is needed, it should be retrieved before pop_back() is called.
         */
        void
            pop_back() _GLIBCXX_NOEXCEPT
        {
            this->_M_erase(iterator(this->_M_impl._M_node._M_prev));
        }

#if __cplusplus >= 201103L
        /**
         *  @brief  Constructs object in %list before specified iterator.
         *  @param  __position  A const_iterator into the %list.
         *  @param  __args  Arguments.
         *  @return  An iterator that points to the inserted data.
         *
         *  This function will insert an object of type T constructed
         *  with T(std::forward<Args>(args)...) before the specified
         *  location.  Due to the nature of a %list this operation can
         *  be done in constant time, and does not invalidate iterators
         *  and references.
         */
        template<typename... _Args>
        iterator
            emplace(const_iterator __position, _Args&&... __args);

        /**
         *  @brief  Inserts given value into %list before specified iterator.
         *  @param  __position  A const_iterator into the %list.
         *  @param  __x  Data to be inserted.
         *  @return  An iterator that points to the inserted data.
         *
         *  This function will insert a copy of the given value before
         *  the specified location.  Due to the nature of a %list this
         *  operation can be done in constant time, and does not
         *  invalidate iterators and references.
         */
        iterator
            insert(const_iterator __position, const value_type& __x);
#else
        /**
         *  @brief  Inserts given value into %list before specified iterator.
         *  @param  __position  An iterator into the %list.
         *  @param  __x  Data to be inserted.
         *  @return  An iterator that points to the inserted data.
         *
         *  This function will insert a copy of the given value before
         *  the specified location.  Due to the nature of a %list this
         *  operation can be done in constant time, and does not
         *  invalidate iterators and references.
         */
        iterator
            insert(iterator __position, const value_type& __x);
#endif

#if __cplusplus >= 201103L
        /**
         *  @brief  Inserts given rvalue into %list before specified iterator.
         *  @param  __position  A const_iterator into the %list.
         *  @param  __x  Data to be inserted.
         *  @return  An iterator that points to the inserted data.
         *
         *  This function will insert a copy of the given rvalue before
         *  the specified location.  Due to the nature of a %list this
         *  operation can be done in constant time, and does not
         *  invalidate iterators and references.
          */
        iterator
            insert(const_iterator __position, value_type&& __x)
        {
            return emplace(__position, std::move(__x));
        }

        /**
         *  @brief  Inserts the contents of an initializer_list into %list
         *          before specified const_iterator.
         *  @param  __p  A const_iterator into the %list.
         *  @param  __l  An initializer_list of value_type.
         *  @return  An iterator pointing to the first element inserted
         *           (or __position).
         *
         *  This function will insert copies of the data in the
         *  initializer_list @a l into the %list before the location
         *  specified by @a p.
         *
         *  This operation is linear in the number of elements inserted and
         *  does not invalidate iterators and references.
         */
        iterator
            insert(const_iterator __p, initializer_list<value_type> __l)
        {
            return this->insert(__p, __l.begin(), __l.end());
        }
#endif

#if __cplusplus >= 201103L
        /**
         *  @brief  Inserts a number of copies of given data into the %list.
         *  @param  __position  A const_iterator into the %list.
         *  @param  __n  Number of elements to be inserted.
         *  @param  __x  Data to be inserted.
         *  @return  An iterator pointing to the first element inserted
         *           (or __position).
         *
         *  This function will insert a specified number of copies of the
         *  given data before the location specified by @a position.
         *
         *  This operation is linear in the number of elements inserted and
         *  does not invalidate iterators and references.
         */
        iterator
            insert(const_iterator __position, size_type __n, const value_type& __x);
#else
        /**
         *  @brief  Inserts a number of copies of given data into the %list.
         *  @param  __position  An iterator into the %list.
         *  @param  __n  Number of elements to be inserted.
         *  @param  __x  Data to be inserted.
         *
         *  This function will insert a specified number of copies of the
         *  given data before the location specified by @a position.
         *
         *  This operation is linear in the number of elements inserted and
         *  does not invalidate iterators and references.
         */
        void
            insert(iterator __position, size_type __n, const value_type& __x)
        {
            list __tmp(__n, __x, get_allocator());
            splice(__position, __tmp);
        }
#endif

#if __cplusplus >= 201103L
        /**
         *  @brief  Inserts a range into the %list.
         *  @param  __position  A const_iterator into the %list.
         *  @param  __first  An input iterator.
         *  @param  __last   An input iterator.
         *  @return  An iterator pointing to the first element inserted
         *           (or __position).
         *
         *  This function will insert copies of the data in the range [@a
         *  first,@a last) into the %list before the location specified by
         *  @a position.
         *
         *  This operation is linear in the number of elements inserted and
         *  does not invalidate iterators and references.
         */
        template<typename _InputIterator,
            typename = std::_RequireInputIter<_InputIterator>>
            iterator
            insert(const_iterator __position, _InputIterator __first,
                _InputIterator __last);
#else
        /**
         *  @brief  Inserts a range into the %list.
         *  @param  __position  An iterator into the %list.
         *  @param  __first  An input iterator.
         *  @param  __last   An input iterator.
         *
         *  This function will insert copies of the data in the range [@a
         *  first,@a last) into the %list before the location specified by
         *  @a position.
         *
         *  This operation is linear in the number of elements inserted and
         *  does not invalidate iterators and references.
         */
        template<typename _InputIterator>
        void
            insert(iterator __position, _InputIterator __first,
                _InputIterator __last)
        {
            list __tmp(__first, __last, get_allocator());
            splice(__position, __tmp);
        }
#endif

        /**
         *  @brief  Remove element at given position.
         *  @param  __position  Iterator pointing to element to be erased.
         *  @return  An iterator pointing to the next element (or end()).
         *
         *  This function will erase the element at the given position and thus
         *  shorten the %list by one.
         *
         *  Due to the nature of a %list this operation can be done in
         *  constant time, and only invalidates iterators/references to
         *  the element being removed.  The user is also cautioned that
         *  this function only erases the element, and that if the element
         *  is itself a pointer, the pointed-to memory is not touched in
         *  any way.  Managing the pointer is the user's responsibility.
         */
        iterator
#if __cplusplus >= 201103L
            erase(const_iterator __position) noexcept;
#else
            erase(iterator __position);
#endif

        /**
         *  @brief  Remove a range of elements.
         *  @param  __first  Iterator pointing to the first element to be erased.
         *  @param  __last  Iterator pointing to one past the last element to be
         *                erased.
         *  @return  An iterator pointing to the element pointed to by @a last
         *           prior to erasing (or end()).
         *
         *  This function will erase the elements in the range @a
         *  [first,last) and shorten the %list accordingly.
         *
         *  This operation is linear time in the size of the range and only
         *  invalidates iterators/references to the element being removed.
         *  The user is also cautioned that this function only erases the
         *  elements, and that if the elements themselves are pointers, the
         *  pointed-to memory is not touched in any way.  Managing the pointer
         *  is the user's responsibility.
         */
        iterator
#if __cplusplus >= 201103L
            erase(const_iterator __first, const_iterator __last) noexcept
#else
            erase(iterator __first, iterator __last)
#endif
        {
            while (__first != __last)
                __first = erase(__first);
            return __last._M_const_cast();
        }

        /**
         *  @brief  Swaps data with another %list.
         *  @param  __x  A %list of the same element and allocator types.
         *
         *  This exchanges the elements between two lists in constant
         *  time.  Note that the global std::swap() function is
         *  specialized such that std::swap(l1,l2) will feed to this
         *  function.
         */
        void
            swap(list& __x)
        {
            __detail::_List_node_base::swap(this->_M_impl._M_node,
                __x._M_impl._M_node);

            size_t __xsize = __x._M_get_size();
            __x._M_set_size(this->_M_get_size());
            this->_M_set_size(__xsize);

            // _GLIBCXX_RESOLVE_LIB_DEFECTS
            // 431. Swapping containers with unequal allocators.
            std::__alloc_swap<typename _Base::_Node_alloc_type>::
                _S_do_it(_M_get_Node_allocator(), __x._M_get_Node_allocator());
        }

        /**
         *  Erases all the elements.  Note that this function only erases
         *  the elements, and that if the elements themselves are
         *  pointers, the pointed-to memory is not touched in any way.
         *  Managing the pointer is the user's responsibility.
         */
        void
            clear() _GLIBCXX_NOEXCEPT
        {
            _Base::_M_clear();
            _Base::_M_init();
        }

        // [23.2.2.4] list operations
        /**
         *  @brief  Insert contents of another %list.
         *  @param  __position  Iterator referencing the element to insert before.
         *  @param  __x  Source list.
         *
         *  The elements of @a __x are inserted in constant time in front of
         *  the element referenced by @a __position.  @a __x becomes an empty
         *  list.
         *
         *  Requires this != @a __x.
         */
        void
#if __cplusplus >= 201103L
            splice(const_iterator __position, list&& __x) noexcept
#else
            splice(iterator __position, list& __x)
#endif
        {
            if (!__x.empty())
            {
                _M_check_equal_allocators(__x);

                this->_M_transfer(__position._M_const_cast(),
                    __x.begin(), __x.end());

                this->_M_inc_size(__x._M_get_size());
                __x._M_set_size(0);
            }
        }

#if __cplusplus >= 201103L
        void
            splice(const_iterator __position, list& __x) noexcept
        {
            splice(__position, std::move(__x));
        }
#endif

#if __cplusplus >= 201103L
        /**
         *  @brief  Insert element from another %list.
         *  @param  __position  Const_iterator referencing the element to
         *                      insert before.
         *  @param  __x  Source list.
         *  @param  __i  Const_iterator referencing the element to move.
         *
         *  Removes the element in list @a __x referenced by @a __i and
         *  inserts it into the current list before @a __position.
         */
        void
            splice(const_iterator __position, list&& __x, const_iterator __i) noexcept
#else
        /**
         *  @brief  Insert element from another %list.
         *  @param  __position  Iterator referencing the element to insert before.
         *  @param  __x  Source list.
         *  @param  __i  Iterator referencing the element to move.
         *
         *  Removes the element in list @a __x referenced by @a __i and
         *  inserts it into the current list before @a __position.
         */
        void
            splice(iterator __position, list& __x, iterator __i)
#endif
        {
            iterator __j = __i._M_const_cast();
            ++__j;
            if (__position == __i || __position == __j)
                return;

            if (this != &__x)
                _M_check_equal_allocators(__x);

            this->_M_transfer(__position._M_const_cast(),
                __i._M_const_cast(), __j);

            this->_M_inc_size(1);
            __x._M_dec_size(1);
        }

#if __cplusplus >= 201103L
        /**
         *  @brief  Insert element from another %list.
         *  @param  __position  Const_iterator referencing the element to
         *                      insert before.
         *  @param  __x  Source list.
         *  @param  __i  Const_iterator referencing the element to move.
         *
         *  Removes the element in list @a __x referenced by @a __i and
         *  inserts it into the current list before @a __position.
         */
        void
            splice(const_iterator __position, list& __x, const_iterator __i) noexcept
        {
            splice(__position, std::move(__x), __i);
        }
#endif

#if __cplusplus >= 201103L
        /**
         *  @brief  Insert range from another %list.
         *  @param  __position  Const_iterator referencing the element to
         *                      insert before.
         *  @param  __x  Source list.
         *  @param  __first  Const_iterator referencing the start of range in x.
         *  @param  __last  Const_iterator referencing the end of range in x.
         *
         *  Removes elements in the range [__first,__last) and inserts them
         *  before @a __position in constant time.
         *
         *  Undefined if @a __position is in [__first,__last).
         */
        void
            splice(const_iterator __position, list&& __x, const_iterator __first,
                const_iterator __last) noexcept
#else
        /**
         *  @brief  Insert range from another %list.
         *  @param  __position  Iterator referencing the element to insert before.
         *  @param  __x  Source list.
         *  @param  __first  Iterator referencing the start of range in x.
         *  @param  __last  Iterator referencing the end of range in x.
         *
         *  Removes elements in the range [__first,__last) and inserts them
         *  before @a __position in constant time.
         *
         *  Undefined if @a __position is in [__first,__last).
         */
        void
            splice(iterator __position, list& __x, iterator __first,
                iterator __last)
#endif
        {
            if (__first != __last)
            {
                if (this != &__x)
                    _M_check_equal_allocators(__x);

                size_t __n = this->_M_distance(__first._M_node, __last._M_node);
                this->_M_inc_size(__n);
                __x._M_dec_size(__n);

                this->_M_transfer(__position._M_const_cast(),
                    __first._M_const_cast(),
                    __last._M_const_cast());
            }
        }

#if __cplusplus >= 201103L
        /**
         *  @brief  Insert range from another %list.
         *  @param  __position  Const_iterator referencing the element to
         *                      insert before.
         *  @param  __x  Source list.
         *  @param  __first  Const_iterator referencing the start of range in x.
         *  @param  __last  Const_iterator referencing the end of range in x.
         *
         *  Removes elements in the range [__first,__last) and inserts them
         *  before @a __position in constant time.
         *
         *  Undefined if @a __position is in [__first,__last).
         */
        void
            splice(const_iterator __position, list& __x, const_iterator __first,
                const_iterator __last) noexcept
        {
            splice(__position, std::move(__x), __first, __last);
        }
#endif

        /**
         *  @brief  Remove all elements equal to value.
         *  @param  __value  The value to remove.
         *
         *  Removes every element in the list equal to @a value.
         *  Remaining elements stay in list order.  Note that this
         *  function only erases the elements, and that if the elements
         *  themselves are pointers, the pointed-to memory is not
         *  touched in any way.  Managing the pointer is the user's
         *  responsibility.
         */
        void
            remove(const _Tp& __value);

        /**
         *  @brief  Remove all elements satisfying a predicate.
         *  @tparam  _Predicate  Unary predicate function or object.
         *
         *  Removes every element in the list for which the predicate
         *  returns true.  Remaining elements stay in list order.  Note
         *  that this function only erases the elements, and that if the
         *  elements themselves are pointers, the pointed-to memory is
         *  not touched in any way.  Managing the pointer is the user's
         *  responsibility.
         */
        template<typename _Predicate>
        void
            remove_if(_Predicate);

        /**
         *  @brief  Remove consecutive duplicate elements.
         *
         *  For each consecutive set of elements with the same value,
         *  remove all but the first one.  Remaining elements stay in
         *  list order.  Note that this function only erases the
         *  elements, and that if the elements themselves are pointers,
         *  the pointed-to memory is not touched in any way.  Managing
         *  the pointer is the user's responsibility.
         */
        void
            unique();

        /**
         *  @brief  Remove consecutive elements satisfying a predicate.
         *  @tparam _BinaryPredicate  Binary predicate function or object.
         *
         *  For each consecutive set of elements [first,last) that
         *  satisfy predicate(first,i) where i is an iterator in
         *  [first,last), remove all but the first one.  Remaining
         *  elements stay in list order.  Note that this function only
         *  erases the elements, and that if the elements themselves are
         *  pointers, the pointed-to memory is not touched in any way.
         *  Managing the pointer is the user's responsibility.
         */
        template<typename _BinaryPredicate>
        void
            unique(_BinaryPredicate);

        /**
         *  @brief  Merge sorted lists.
         *  @param  __x  Sorted list to merge.
         *
         *  Assumes that both @a __x and this list are sorted according to
         *  operator<().  Merges elements of @a __x into this list in
         *  sorted order, leaving @a __x empty when complete.  Elements in
         *  this list precede elements in @a __x that are equal.
         */
#if __cplusplus >= 201103L
        void
            merge(list&& __x);

        void
            merge(list& __x)
        {
            merge(std::move(__x));
        }
#else
        void
            merge(list& __x);
#endif

        /**
         *  @brief  Merge sorted lists according to comparison function.
         *  @tparam _StrictWeakOrdering Comparison function defining
         *  sort order.
         *  @param  __x  Sorted list to merge.
         *  @param  __comp  Comparison functor.
         *
         *  Assumes that both @a __x and this list are sorted according to
         *  StrictWeakOrdering.  Merges elements of @a __x into this list
         *  in sorted order, leaving @a __x empty when complete.  Elements
         *  in this list precede elements in @a __x that are equivalent
         *  according to StrictWeakOrdering().
         */
#if __cplusplus >= 201103L
        template<typename _StrictWeakOrdering>
        void
            merge(list&& __x, _StrictWeakOrdering __comp);

        template<typename _StrictWeakOrdering>
        void
            merge(list& __x, _StrictWeakOrdering __comp)
        {
            merge(std::move(__x), __comp);
        }
#else
        template<typename _StrictWeakOrdering>
        void
            merge(list& __x, _StrictWeakOrdering __comp);
#endif

        /**
         *  @brief  Reverse the elements in list.
         *
         *  Reverse the order of elements in the list in linear time.
         */
        void
            reverse() _GLIBCXX_NOEXCEPT
        {
            this->_M_impl._M_node._M_reverse();
        }

        /**
         *  @brief  Sort the elements.
         *
         *  Sorts the elements of this list in NlogN time.  Equivalent
         *  elements remain in list order.
         */
        void
            sort();

        /**
         *  @brief  Sort the elements according to comparison function.
         *
         *  Sorts the elements of this list in NlogN time.  Equivalent
         *  elements remain in list order.
         */
        template<typename _StrictWeakOrdering>
        void
            sort(_StrictWeakOrdering);

    protected:
        // Internal constructor functions follow.

        // Called by the range constructor to implement [23.1.1]/9

        // _GLIBCXX_RESOLVE_LIB_DEFECTS
        // 438. Ambiguity in the "do the right thing" clause
        template<typename _Integer>
        void
            _M_initialize_dispatch(_Integer __n, _Integer __x, __true_type)
        {
            _M_fill_initialize(static_cast<size_type>(__n), __x);
        }

        // Called by the range constructor to implement [23.1.1]/9
        template<typename _InputIterator>
        void
            _M_initialize_dispatch(_InputIterator __first, _InputIterator __last,
                __false_type)
        {
            for (; __first != __last; ++__first)
#if __cplusplus >= 201103L
                emplace_back(*__first);
#else
                push_back(*__first);
#endif
        }

        // Called by list(n,v,a), and the range constructor when it turns out
        // to be the same thing.
        void
            _M_fill_initialize(size_type __n, const value_type& __x)
        {
            for (; __n; --__n)
                push_back(__x);
        }

#if __cplusplus >= 201103L
        // Called by list(n).
        void
            _M_default_initialize(size_type __n)
        {
            for (; __n; --__n)
                emplace_back();
        }

        // Called by resize(sz).
        void
            _M_default_append(size_type __n);
#endif

        // Internal assign functions follow.

        // Called by the range assign to implement [23.1.1]/9

        // _GLIBCXX_RESOLVE_LIB_DEFECTS
        // 438. Ambiguity in the "do the right thing" clause
        template<typename _Integer>
        void
            _M_assign_dispatch(_Integer __n, _Integer __val, __true_type)
        {
            _M_fill_assign(__n, __val);
        }

        // Called by the range assign to implement [23.1.1]/9
        template<typename _InputIterator>
        void
            _M_assign_dispatch(_InputIterator __first, _InputIterator __last,
                __false_type);

        // Called by assign(n,t), and the range assign when it turns out
        // to be the same thing.
        void
            _M_fill_assign(size_type __n, const value_type& __val);


        // Moves the elements from [first,last) before position.
        void
            _M_transfer(iterator __position, iterator __first, iterator __last)
        {
            __position._M_node->_M_transfer(__first._M_node, __last._M_node);
        }

        // Inserts new element at position given and with value given.
#if __cplusplus < 201103L
        void
            _M_insert(iterator __position, const value_type& __x)
        {
            _Node* __tmp = _M_create_node(__x);
            __tmp->_M_hook(__position._M_node);
            this->_M_inc_size(1);
        }
#else
        template<typename... _Args>
        void
            _M_insert(iterator __position, _Args&&... __args)
        {
            _Node* __tmp = _M_create_node(std::forward<_Args>(__args)...);
            __tmp->_M_hook(__position._M_node);
            this->_M_inc_size(1);
        }
#endif

        // Erases element at position given.
        void
            _M_erase(iterator __position) _GLIBCXX_NOEXCEPT
        {
            this->_M_dec_size(1);
            __position._M_node->_M_unhook();
            _Node* __n = static_cast<_Node*>(__position._M_node);
#if __cplusplus >= 201103L
            _M_get_Node_allocator().destroy(__n);
#else
            _M_get_Tp_allocator().destroy(std::__addressof(__n->_M_data));
#endif
            _M_put_node(__n);
        }

        // To implement the splice (and merge) bits of N1599.
        void
            _M_check_equal_allocators(list& __x) _GLIBCXX_NOEXCEPT
        {
            if (std::__alloc_neq<typename _Base::_Node_alloc_type>::
                _S_do_it(_M_get_Node_allocator(), __x._M_get_Node_allocator()))
                __builtin_abort();
        }
    };
    _GLIBCXX_END_NAMESPACE_CXX11

        /**
         *  @brief  List equality comparison.
         *  @param  __x  A %list.
         *  @param  __y  A %list of the same type as @a __x.
         *  @return  True iff the size and elements of the lists are equal.
         *
         *  This is an equivalence relation.  It is linear in the size of
         *  the lists.  Lists are considered equivalent if their sizes are
         *  equal, and if corresponding elements compare equal.
        */
        template<typename _Tp, typename _Alloc>
    inline bool
        operator==(const list<_Tp, _Alloc>&__x, const list<_Tp, _Alloc>&__y)
    {
        typedef typename list<_Tp, _Alloc>::const_iterator const_iterator;
        const_iterator __end1 = __x.end();
        const_iterator __end2 = __y.end();

        const_iterator __i1 = __x.begin();
        const_iterator __i2 = __y.begin();
        while (__i1 != __end1 && __i2 != __end2 && *__i1 == *__i2)
        {
            ++__i1;
            ++__i2;
        }
        return __i1 == __end1 && __i2 == __end2;
    }

    /**
     *  @brief  List ordering relation.
     *  @param  __x  A %list.
     *  @param  __y  A %list of the same type as @a __x.
     *  @return  True iff @a __x is lexicographically less than @a __y.
     *
     *  This is a total ordering relation.  It is linear in the size of the
     *  lists.  The elements must be comparable with @c <.
     *
     *  See std::lexicographical_compare() for how the determination is made.
    */
    template<typename _Tp, typename _Alloc>
    inline bool
        operator<(const list<_Tp, _Alloc>&__x, const list<_Tp, _Alloc>&__y)
    {
        return std::lexicographical_compare(__x.begin(), __x.end(),
            __y.begin(), __y.end());
    }

    /// Based on operator==
    template<typename _Tp, typename _Alloc>
    inline bool
        operator!=(const list<_Tp, _Alloc>&__x, const list<_Tp, _Alloc>&__y)
    {
        return !(__x == __y);
    }

    /// Based on operator<
    template<typename _Tp, typename _Alloc>
    inline bool
        operator>(const list<_Tp, _Alloc>&__x, const list<_Tp, _Alloc>&__y)
    {
        return __y < __x;
    }

    /// Based on operator<
    template<typename _Tp, typename _Alloc>
    inline bool
        operator<=(const list<_Tp, _Alloc>&__x, const list<_Tp, _Alloc>&__y)
    {
        return !(__y < __x);
    }

    /// Based on operator<
    template<typename _Tp, typename _Alloc>
    inline bool
        operator>=(const list<_Tp, _Alloc>&__x, const list<_Tp, _Alloc>&__y)
    {
        return !(__x < __y);
    }

    /// See std::list::swap().
    template<typename _Tp, typename _Alloc>
    inline void
        swap(list<_Tp, _Alloc>&__x, list<_Tp, _Alloc>&__y)
    {
        __x.swap(__y);
    }

    _GLIBCXX_END_NAMESPACE_CONTAINER
} // namespace std

#endif /* _STL_LIST_H */
